Messages in this thread Patch in this message | | | From | FUJITA Tomonori <> | Subject | [PATCH] block: fix q->max_segment_size checking in blk_recalc_rq_segments about VMERGE | Date | Tue, 15 Jul 2008 19:44:36 +0900 |
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blk_recalc_rq_segments assumes that any segments can be merged in the case of BIOVEC_VIRT_MERGEABLE && !BIOVEC_VIRT_OVERSIZE. However, an IOMMU can't merge segments if the total length of the segments is larger than max_segment_size (the LLD restriction).
Due to this bug, a LLD may get the larger number of segments than nr_hw_segments because the block layer puts more segments in a request than it should do.
This bug could happen on alpha, parisc, and sparc, which use VMERGE.
Like blk_hw_contig_segment() does, this patch uses hw_seg_size for simplicity, which is a bit larger than an exact value (we don't need BIOVEC_VIRT_START_SIZE here).
Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp> Cc: Jens Axboe <jens.axboe@oracle.com> Cc: Mikulas Patocka <mpatocka@redhat.com> Cc: David Miller <davem@davemloft.net> --- block/blk-merge.c | 3 ++- 1 files changed, 2 insertions(+), 1 deletions(-)
diff --git a/block/blk-merge.c b/block/blk-merge.c index 5efc9e7..39a22f8 100644 --- a/block/blk-merge.c +++ b/block/blk-merge.c @@ -83,7 +83,8 @@ void blk_recalc_rq_segments(struct request *rq) continue; } new_segment: - if (BIOVEC_VIRT_MERGEABLE(bvprv, bv) && + if (hw_seg_size + bv->bv_len <= q->max_segment_size && + BIOVEC_VIRT_MERGEABLE(bvprv, bv) && !BIOVEC_VIRT_OVERSIZE(hw_seg_size + bv->bv_len)) hw_seg_size += bv->bv_len; else { -- 1.5.5.GIT
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